In this study, the facile synthesis and electroluminescent perovskite light-emitting diodes (PeLEDs) of highly luminescent Cs 4 PbBr 6 /CsPbBr 3 nanocomposite has been demonstrated. With the addition of proper antisolvents, the nanocomposite with a production yield of >90% and quantum yield of >85% was readily derived from the transformation of CsPbBr 3 powder. The obtained high quantum yield of the green nanocomposite originated from the fluorescent CsPbBr 3 nanocrystals embedded in the Cs 4 PbBr 6 matrix, which was verified by Xray diffraction, absorption, photoluminescence (PL), and PL excitation spectra. The addition of large cation precursors, such as CsBr and CH(NH 2 ) 2 Br, could contribute to the transformation efficiency and had no influence on the composition of the embedded nanocrystals. Via the thermal evaporation of the nanocomposite, all-inorganic electroluminescent PeLEDs with CuSCN and Cu-doped NiO x (NiO x :Cu) nanoparticles were fabricated and characterized. A maximum luminance of 1780 cd/m 2 and efficiency of 0.43 cd/A were achieved. Thus, the luminescent Cs 4 PbBr 6 /CsPbBr 3 nanocomposite is a promising material for nextgeneration displays and lighting.

A facile synthesis method is proposed for the mass production of high-quality CsPbBr 3 perovskite powder. It is shown that the proposed synthesis protocol is capable of producing polycrystalline CsPbBr 3 powder in quantities greater than 10 g. The derived thin films by thermal evaporation and spin-coating are of compact morphologies (root-mean-square roughness < 4 nm) without voids and pinholes. Moreover, the thin films show obvious photoluminescence (PL) with a narrow (bandwidth < 19 nm) peak centered at ∼520 nm, which is blue-shifted compared with the PL emission of the powder at 542 nm. The powder and the spin-coated film exhibit superior PL stability under long-term ambient conditions and in thermal cycling experiments performed at temperatures up to ∼120 °C. Accordingly, optoelectronic applications including the fabrication and characteristics of the electroluminescence device, the organic–inorganic powder doped with methylammonium and formamidinium ions, and fluorescent greenish-blue quantum dots are also demonstrated. On the basis of these demonstrations, the synthesized CsPbBr 3 perovskite powder can be expected to empower the advances in perovskite-related optoelectronics in the future.